SYNTHESIS AND CHARACTERIZATION OF A HIGH-TEMPERATURE OXIDE LUBRICANT

PbMoO4 is a potential solid lubricant for use at elevated temperatures in oxidizing environments. Pulsed laser deposition (PLD) was utilized to grow thin films of this material because it allows good control ov er film chemistry and crystallinity. Films were grown at different sub strate temperatures in vacuum and in partial pressures of oxygen. The chemistry and crystallinity of the films were evaluated using X-ray ph otoelectron spectroscopy, Raman spectroscopy, and glancing angle X-ray diffraction. Friction coefficients and wear lives were measured using a ball-on-flat tribometer at room temperature and 700 degrees C. Film s deposited in vacuum, at room temperature and at 300 degrees C, were oxygen deficient. To adjust chemistry and crystallinity, films were gr own in a partial pressure of oxygen (i.e. 6.7 x 10(-1) Pa). Stoichiome tric, crystalline films of PbMoO4 were produced when films were grown at 300 degrees C in this environment. PbMoO4 films were lubricious (mu = 0.35) and long lived at 700 degrees C, but at room temperature had high friction and failed quickly. The properties of the films grown at the different conditions are discussed.